Cross roll straightener machine

ABSTRACT

A cross roll machine comprising a housing, upper and lower roll carrier means supported in said housing, upper and lower rolls supported by said roll carrier means, one of said roll carrier means and said housing defining vertically spaced-apart cooperating surfaces disposed so that a load tends to move said surfaces together, further including a plurality of dish springs between said surfaces, and means for preloading said dish springs to maintain a substantially constant spacing between the surfaces under normal load conditions.

United States Patent {72] Inventor William llyarns Bethel Park, Pa. 211App1.No. 794,524 [22] Filed Jan. 28, 1969 [45] Patented July 6, I971[73] Assignee Gulf & Western Industrial Products Company Grand Rapids,Mich.

[541 CROSS ROLL STRAIGHTENER MACHINE 10 Claims, 4 Drawing Figs.

[52] 0.8. CI. 72/99, 72/246 [51] lnt.Cl ..B2lb 19/02, 1321b 31/16 [50]Field of Search 72/164, 162,99,101, 246,111

[56] References Cited UNITED STATES PATENTS 287,659 10/1883 Gifford;72/246 2,168,435 8/1939 Bond 72/246 X 2,182,900 12/1939 Mcllvried et al.72/245 X 2,319,785 5/1943 Abramsen 72/99 2,348,283 5/1944 Dolan 72/2462,729,003 1/1956 Cohn et a1. 72/245 X 2,787,304 4/1957 Brundell et a1.144/208 (E) 3,124,982 3/1964 Neumann 72/21 3,187,536 6/1965 Zolton 72/99Primary Examiner-Milton S. Mehr AtlomeyMeyer, Tilberry and Body PATENTEDJUL6 ma SHEET 1 OF 2 Q o; d THEN? I 1 1 1 I 1 I J Q WILLIAM HYAMSATTORNEYS CROSS ROLL STRAIGHTIENER MACHINE DESCRIPTION The presentinvention relates to load-limiting devices, and particularly to aload-limiting device for a cross roll machine.

Although the invention is particularly applicable to a cross rollmachine, and will be described with reference thereto, it will beappreciated that the invention has broader application with other typesof machines.

A cross roll machine is well known employed for straightening, polishingor derodding tubular workpieces. The machine consists of a plurality ofpairs of rolls, preferably three pairs, aligned along the machine axiswith the upper roll of each pair being oriented at one angle withrespect to the machine axis and the lower roll at a different angle. Theroll surfaces are curved to conform generally with the workpiecesurface, and are rotationally driven. The roll pass center of the middleroll pair is slightly offset vertically from the roll pass centers ofthe receiving and delivering roll pairs so that the workpiece advancesforwardly through a bending arc. Rotation of the rolls causes theworkpiece also to rotate as it advances, this working of the workpieceover its entire length and through all its axes imparting straightnessand eliminating out-of-roundness.

In order to obtain close-tolerance straightness and eliminate allout-of-roundness, it is necessary that the cross roll machine becompletely rigid; that is, that the spacing between upper and lowerrolls be maintained constant during normal loads. ln building a crossroll machine, all of the components of the machine are deliberatelydesigned to avoid elasticity.

In operation, the pass openings between the machines three sets of rollsare carefully adjusted to exactly suit the outside diameter of the roundworkpiece being straightened, to permit its easy entry through the rollpasses; and at the same time cause the upper and lower rolls to grip theworkpiece positively and exert sufficient tractive and rotative contactpressures on the workpiece to advance it longitudinally and spirallythrough the pass openings.

One practice which frequently is employed is the elimination of unwantedovality in tubular workpieces by adjusting the upper and lower crossrolls to a roll opening slightly smaller than the outside diameter ofthe workpiece. This practice may safely be employed with tubularworkpieces having thin, normal or even fairly heavy wall thicknesses,since, as long as the tubular workpieces fall within the machine's ratedoutside diameter size, wall thickness and workpiece material strengthlimits, they can be deformed by pressure between the opposed cross rollsinto a temporary flattened oval shape, from which shape the tubularworkpieces emerge with improved roundness.

Even where the roll pass openings are appreciably smaller than thetubular workpiece outside diameters, those workpieces which can readilybe ovalled by roll pressure can enter without difficulty between theopposed upper and lower cross rolls, particularly if the cross rolls ofthe first or receiving pass are adjusted to a slightly open angularposition so to present to the oncoming front end of the tubularworkpiece a funnelshaped entrance path.

However, the cross roll machines have heretofore been limited to usewith readily deformable workpieces, and generally are not recommendedfor straightening, polishing or derodding extra heavy-wall tubularworkpieces of highstrength material; or solid-bar workpieces. The reasonfor this is that extreme care must be exercised in accurately adjustingthe cross roll openings to suit the workpieces of this category, and ifan oversized workpiece or one of extreme unevenness in this category isforced between the cross rolls, the machine being extremely rigid, suchworkpieces being not readily deformable to an oval shape could uponentering immediately exert between the opposed cross rolls a separatingforce of The problem is particularly serious with respect to the rollneck portions and roll neck bearings of the rolls. The rolls at oppositeends of the roll body are supported by axially extending neck portions,rotating in frame roll neck bearings. To provide adequate clearances ina cross roll machine, particularly between the roll bearing housings andthe workpiece, the roll neck bearings must be as close as possible tothe roll bodies limiting the permissible radii of the fillets betweenthe roll necks and bodies, creating stress points at these radii. I

it is important to note that the problem is acute only with solid-bar orheavy-wall, high-strength, material of slightly oversized diameter.workpieces having an outside diameter considerably larger than the rollpass openings will refuse to enter the constricted space between thecross rolls, since they are not readily deformable. This refusal toenter occurs even when the cross rolls are angularly adjusted so as topresent to the front end of the workpiece a funnel-shaped opening.

it is an object of the present invention to overcome the abovelimitation of cross roll machines, and in particular to provide a crossroll machine capable of safely straightening, polishing or deroddingextra heavy-wall tubular workpieces of high-strength material andsolid-bar workpieces, in addition to tubular workpieces capable of beingreadily deformable to an oval shape.

it is further an object of the present. invention to provide aload-limiting device for a cross roll straightener which is simple andinexpensive, and in addition which has the characteristic of functioningas a rigid connection or member under all but an overload condition,providing a short rapid almost instantaneous relief stroke suitable forslightly oversized pieces when an overload condition occurs.

in accordance with the present invention, there is provided a cross rollmachine comprising a housing, upper and lower roll carrier meanssupported in said housing, upper and lower rolls supported by said rollcarrier means, one of said roll carrier means and said housing definingvertically spaced-apart cooperating surfaces disposed so at a load tendsto move said surfaces together, further including a plurality of dishsprings between said surfaces, and means for preloading said dishsprings to maintain a substantially constant spacing between saidsurfaces under normal load conditions.

Preferably, the upper roll carrier means is vertically adjustablerelative to the housing and comprises a roll carrier frame which isrotatable about a vertical axis in the housing, including adjustingmeans for raising and lowering the frame, said adjusting meanscomprising a vertical downwardly extending threaded shaft and an annularscrew box member threaded onto said shaft. The roll carrier framedefines a vertically oriented bore receiving the screw box member and anupwardly facing seat which is spaced from a downwardly facing surface ofthe screw box member, cooperating therewith to define that space whichis compressed in the event of an overload condition.

Preferably, at least two pairs of dish springs are used, the springs ineach pair being seated so that the concave surfaces thereof are facingeach other, the pairs being in back-toback relationship.

The invention and advantages thereof will become apparent upon furtherconsideration of the specification, with reference to the accompanyingdrawings, in which FIG. 11 is an elevation view of a cross roll machineillustrating the concepts of the invention;

FIG. 2 is an enlarged cross section view taken along line 2-2 of MG. 1;

MG. 3 is a partial section view taken along line 3-3 of FIG. 2; and

FIG. d is an enlarged partial perspective view of a nest of dish springsin accordance with the invention.

Referring now to the drawings, wherein the showings are for the purposeof illustrating the preferred embodiment of the invention only and notfor the purpose of limiting the same, the Figures show a cross rollstraightener A which is provided with upper and lower housings B and Crespectively. The upper and lower housings support a plurality ofopposed upper and lower roll carrier frames D which in turn support rollpairs R1, R2 and R3.

Referring to the drawings in detail, the cross roll straightener,generally indicated by the letter A, comprises a base 12, below thelower housing C, on which there is supported the components of themachine, many of which are conventional and form no part of thisinvention. The lower housing C is supported directly on the base 12, theupper housing B being held above the lower housing by means of supportcolumns 14 connected to the lower housing. The cross roll straightenerdefines a substantially horizontal longitudinal axis along which tubes,bars or other workpieces of circular cross section are threaded, theworkpieces being engaged in the pass openings between the upper andlower rolls l6 and 18 of the roll pairs R1, R2, and R3, the openingsbetween the rolls being sufficient to accommodate the workpiece butfunctionally engage its surface. In the example illustrated in FIG. 1,the roll pair Rll represents the receiving roll pair, and the roll pairR3 represents the delivering roll pair. The upper rolls to of each ofthese roll pairs are arranged in the same horizontal plane and the lowerrolls 18 of the two roll pairs are arranged in a plane which issubstantially parallel to the upper plane; the center roll pair beingdisplaced slightly upwardly with respect to the receiving and deliveringroll pair to produce a bending are through which the rotating axiallymoving workpieces extend. This rotational and axial movement, through abending arc, flexes and rounds the workpiece along its entire length andthrough all of its axes to impart close-tolerance straightness to theworkpiece and eliminate out-of-roundness.

EAch roll of each roll pair is provided with a concave surface 20 whichconform generally with the surface of the workpiece, the upper roll toof each pair being angled at one angle with respect to the machine axis,the lower roll lb of each roll pair being angled at a different angle,,so that looking from the top down, the axes of the roll pairs arecrossed. The rolls preferably are individually driven by drive means 2 3which are not a part of this invention, and rotation of the concavesurfaces of the rolls, the latter angled with respect to the directionof travel of the workpiece, causes the desired rotational and axialmovement of the latter.

The shape of the rolls is shown in FIGS. 2 and 3 in more detail, eachroll comprising a roll body 26 of circular cross section having agenerally constricted center section 28 so that the roll surface profilein an elevation view is concave. Extending axially from the roll body atopposite ends thereof are opposed necks 30 and 32 which are ofsubstantially lesser diameter than the roll body 26.

Referring to FIG. 2, the upper rolls 16 are supported so that they canbe moved vertically up or down, the lower rolls if being fixedly heldrelative to the lower housing C.

To support the upper rolls, the necks 30 and 32 of the rolls arecontained in roll neck bearing housings 34 and 36 which are part of aninverted U-shaped roll carrier frame yoke 38. Annular ball bearings 40and 42 permit rotation of the roll necks within the roll bearinghousings.

The yoke 38 is an integral part of a roll carrier frame 34 which isprovided with a cylindrical carrier frame body 46 extending upwardlyinto a vertically extending cylindrical socket 48 formed within thecross roll machine upper housing B. This socket is sufficiently deep toaccommodate substantially all of the carrier frame body 46, and slidablyreceives the body with a close sliding fit to hold the body againstlateral displacement.

The carrier frame body in turn is provided with an axial bore 50 whichextends all the way through it and receives a shank 52 of an adjustingmechanism 54. The latter is threaded along its lower end 56 to receivean internally threaded nutlikc screw box member 58, rotation of theadjusting mechanism shank 52 relative to the screw box member causingthe latter to move upwardly or downwardly on the shank threaded end.

The screw box member is secured with the carrier frame body 46, in anannular cavity 60 in the upper end as thereof coaxial with but of largerdiameter than the bore 50. The

lower end of the cavity 60 terminates in a seat 64 which is spaced frombut opposite to the lower end surface 66 of the screw box member 58, todefine an annular space 68. At its upper end, the cavity is bridged overwith a washerlike retaining ring 70, bolted to a shoulder portion 72 ofthe carrier frame body by a plurality of spaced bolts 74, the upper end75 of the screw box member bearing against the underside of ring 70.

To prevent the screw box member 58 from rotating with rotation of theadjusting mechanism shank 52, a plurality of keys 76 are positionedbetween the retaining ring 70 and the screw box member 58, seated intoboth, so that the screw box member does not turn within the carrierframe body 46.

To support the adjusting mechanism in the housing B, the shank 52 of themechanism is provided with an upper end 78 which penetrates an upperportion of the housing, and a roller thrust bearing 80 around the shankupper end 78 seats between an annular shoulder 82 on the shank and theupper surface 84 of the housing. The roller bearing supports the weightof the roll carrier frame and rolls, and permits the ad justingmechanism to turn within the housing.

Spaced from the roller bearing 80 is a second annular bearing 86 on theshank upper end engaging the underside or upper inner surface 88 of thehousing B. When an upward force is exerted against the upper roll, thisforce is transmitted through the roll carrier frame body 46 onto thescrew box member 58 (in a manner to be described), onto the adjustingmechanism shank 52, and through the bearing 86 against the surface 88 ofthe housing.

To transfer this upward force from the carrier frame body 46 to thescrew box member, in accordance with the present invention, a pluralityof dish springs 90 are positioned in the annular space 63 between thescrew box member and the roll carrier seat 64. These dish springs areillustrated in detail in FIG. 4, and comprise washerlike members havinga hollowed (or concave) surface Q2 between inner and outer circularedges 94 and 96, and a back (or convex) surface 97. In the presentinvention, it is contemplated that they be utilized in pairs, with thedished hollowed surfaces facing each other and with the inner and outeredges of each spring member bearing against the corresponding edges ofanother spring member. In the embodiment illustrated, two pairs of thedish springs are utilized with the back surface 97 of one spring of onepair bearing against the back surface 97 of one spring of the otherpair.

The dish spring is a well-known type of spring, manufactured under anumber of trademarks, one suitable for use in accordance with thepresent invention being the Belleville (registered trademark) spring.

Each spring nest must act as a solid nondeflecting roll support memberunder all load conditions anticipated in normal straightening service.This requires that the dish springs be 'precompressed, and this isaccomplished by placing a plurality of shims as between the retainingring 70 and the carrier frame body shoulder '72, the bolts 74 which holdthe retaining ring to the carrier frame body penetrating the shims.Depending upon the number of shims used, the carrier frame body 416 islowered a predetermined amount relative to the screw box member 58, theprecompression being increased by simply reducing the number of shimsforcing the screw box member downwardly in cavity 60 reducing the depthof the annular space 68 between the screw box member and the annularseat 64,

In operation, the dish springs are subjected to a predetermined amountof precompression by adjustment of the number of shims used, and afterthis, the vertical height of the upper roll relative to the lower roll,or the pass opening between the rolls is adjusted simply by rotating thehandle 102 of the adjusting mechanism raising or lowering the screw boxmember member 58 relative to the adjusting mechanism shank 52. This inturn raises or lowers the carrier frame body and roll.

In the event an oversized piece which cannot readily be ovalled isaccepted in the roll pass opening between opposed cross rolls, theexcess load is transmitted through the roll necks and carrier frame intothe dish springs, collapsing the latter in the very short upward strokewhich relieves the overload condition.

The unique suitability of the dish springs in the above application orservice is illustrated in the following example which shows the mannerin which the given characteristics of the dish springs exactly matchrequirements.

EXAMPLE Critical factors are deflection, preload, and maximum load,capabilities of the spring nest.

Experience has shown that nondeformable workpieces having outsidediameters measuring more than approximately 107.5 percent of theroll-opening dimension will not enter between the cross rolls.Accordingly, only nondeforrnable workpieces of outside diameter greaterthan 100 percent but less than approximately 107.5 percent of theroll-opening dimension are capable of producing destructive overloads.

In the example under consideration, the machine maximum ratednondeformable workpiece outside diameter is 0.750 inch. This means thatthe spring nest must be capable of relief deflection of at least 0.056inch (0.750 x 0.075 inch). To provide extra insurance against possibleinaccuracies in parts, dimensions or spring characteristics, a largerdeflection capability of 0.125 inch is desirable.

The cross roll machine also is provided with a rated maximum forceexerted on one bending roll during bend straightening of a steel bar(0.75 inch diameter, minimum yield strength of 70,000 p.s.i.) calculatedat 1,440 pounds. This means that the spring nest must be capable ofbeing preloaded so that it is completely rigid and acts as a solidnondeflecting roll support member up to 1,440 pounds load. It furthermeans that the spring nest should have at least 0.125 inch deflectioncapability after being deflected by the 1,440 pounds preload.

The rated maximum force for each neck will be half of 1,440 pounds or720 pounds.

The maximum design load capacity ofa roll, defined as that load whichcreates a maximum ultimate fiber stress of 45,000 p.s.i. in tension inthe radius at the junction between the roll neck and roll body (which45,000 p.s.i. is in turn one-third of 135,000 p.s.i. maximum yieldstrength of the roll metal), is calculated at 2,7000 pounds or 1,350pounds on each roll neck at the centerline of each roll neck supportbearing.

Calculations show that the above roll load capacity of 2,700 poundsaffords a 6 to 1 safety factor over normal loading up to 1,440 pounds,and further is safely within the rated combined dynamic capacity of therolls antifriction bearings (calculated at 4,730 pounds).

In any event, the spring nest must have a deflection and loadingcapability such that at maximum (flat) deflection, the load force ornest capacity is equal to or slightly greater than 2,700 pounds.

The following calculations illustrate how the above criteria are met.

The spring selected had the following characteristics: o.d. 3% inches,i.d. 1 9/16 inches, R (radius convex side) =50 percent of o.d. 1.5625inches, R (radius concave side) 0.95 R =0.95 x 1.562 inches= 1.483inches Number of springsin series-per nest=4 Each spring disc:thicknesst= .134"

Each spring disc: maximum defiectionh (free height to fiat height)=.0625

Eacl spring disc: free height=t+h=.134=.0625"= Overall nest freeheight=4 (.134+.0625) =.786

Overall nest flat height 4X .134: .536

Overall nest total deflection=4.h=4 .0625=.250

The flat maximum capacity P or that force required to flatten the nest,is calculated to be 3,262 pounds. This is ca1culated using the formulaEht P2: 311m Wherein E modulus of elasticity 30,000,000; M o.d./id.ratio factor= 0.689

For preload of 1440 lbs, nest deflection f Preload nest height .786 .110.676 Reserve nest deflection=4h-f= .250 .110= .140

The reserve nest deflection of 0:140 inch after 616i? 7 deflection is 12percent greater that the desired minimum amount of working deflection of0.124 inch, and therefore is clearly satisfactory.

In that the maximum flat capacity value of P (3,262 pounds) is onlyslightly greater than the load capacity of the roll (2,700 pounds), itis apparent that the maximum relief deflection likely to occur (0.056inch) caused by a 1.075 percent oversized workpiece, will occur at aspring load value, calculated to be 2,166 pounds, well below the 2,700pounds; roll capacity but of course, well above the 1,440 poundspreload.

Advantages of the invention should be apparent. Dimensionwise, the nestof springs is conveniently assembled into the adjusting mechanism forthe upper roll. The device acts as a solid nondeflecting roll supportmember under all load conditions which might be anticipated in normalstraightening service, and at the same time, the nest provides theunique short relief stroke required for cross roll, solid-bar orheavy-wall tube straightening. It will be recalled that no relief strokeis required for workpieces so large that the openings between the crossrolls refuse to accept them. Finally the small-dimensioned springs havemore than adequate relief load capacity.

Although the invention has been described with reference to specificembodiments, variations within the scope of the following claims will beapparent to those skilled in art.

What I claim is:

I. In a roll machine including a housing, a roll carrier frame supportedwithin said housing, and a roll supported by said roll carrier frame,the improvement comprising adjusting means for vertically adjusting saidroll carrier frame;

said roll carrier frame and adjusting means presenting verticallyspaced-apart cooperating surfaces, and means structurally associatedwith said surfaces so that the imposition of a load on said roll tendsto move said surfaces together; and

a plurality of dish spring means between said surfaces having astiffness sufficient to maintain the spacing rigidly between saidsurfaces under normal load conditions and to yield under overloadconditions.

2. A cross roll straightener machine including a machine axis alongwhich cylindrical stock is threaded;

a plurality of opposed upper and lower rolls of roll pairs arrangedlongitudinally along said axis, the upper rolls being differently angledwith respect to the machine axis than the lower rolls;

said machine comprising upper and lower housings for said upper andlower rolls;

a plurality of roll carrier frames supported in said upper housingsupporting said upper rolls;

adjusting means for vertically adjusting said roll carrier frames;

said roll carrier frames and adjusting means presenting verticallyspaced-apart cooperating surfaces, and means structurally associatedwith said surfaces so that the imposition of a load on said upper rollstends to move said surfaces together;

a plurality of assemblies of dish spring means between said surfaces,each assembly having a stiffness sufficient to maintain the spacingrigidly between the surfaces under normal load conditions and to yieldunder overload conditions.

3. A cross roll straightener machine including a machine axis alongwhich cylindrical stock is threaded;

a plurality of opposed upper and lower rolls of roll pairs arrangedlongitudinally along said axis, the upper rolls being differently angledwith respect to the machine axis than the lower rolls;

said machine comprising upper and lower housings for said upper andlower rolls;

a plurality of roll carrier frames supported in said upper housingsupporting said upper rolls;

adjusting means for vertically adjusting said roll carrier frames, saidadjusting means comprising a vertically extending threaded shank;

a nutlike screw box member threaded onto said shank;

each of said roll carrier frames comprising a cavity to receive saidscrew box member;

said screw box member defining a lower surface and said cavity definingan upwardly facing scat surface spaced from said lower surface; a

said roll carrier frames and adjusting means presenting verticallyspaced-apart cooperating surfaces, and means structurally associatedwith said surfaces so that the imposition of a load on said upper rollstends to move said surfaces together; and

a plurality of assemblies of dish spring means between said surfaces,each assembly having a stiffness sufficient to maintain the spacingrigidly between the surfaces under normal load conditions and to yieldunder overload conditlons, and

said dish springs being disposed between said roll carrier seat and saidscrew box member lower surface, and encompassing said adjusting meansshank.

4. The machine according to claim 3 wherein said roll carrier framefurther comprises a retaining ring connected to said roll carrier frameto bridge said cavity above the screw box member whereby said memberbears against said retaining 8. ring;

means between said roll carrier frame and said retaining ring to effecta predetermined amount of precompression of the dish springs ontightening the retaining ring to the roll carrier frame.

5. The machine of claim 4 wherein said roll carrier frame defines anupwardly facing shoulder further including bolt means fastening theretaining ring to said shoulder, said means to effect a predeterminedamount of precompression comprising a plurality of shims between theshoulder and retaining ring.

6. The machine of claim 4 further including means to prevent therotation of said screw box member relative to the roll carrier frame.

7. The machine of claim 2 wherein said stand of rolls includes threeroll pairs spaced on close centers for precision straightening,

said roll carrier frames each comprising a yoke, said rolls comprising abody and oppositely extending neck portions seated in said carrier frameyokes, the neck portions being of small diameter to permit clearancebetween said yokes and a workpiece, and limiting the radius of thefillets between the neck portions and roll body to a comarativel smalldimension. I 8. he mac me of claim 2 wherein said dish springs areannular washerlike members comprising inner and outer circular edgesincluding oppositely facing hollowed and back surfaces between saidedges, said members being arranged in pairs with the hollowed surface ofone member facing the hollowed surface of another member, and the outeredges of said members being in contact.

9. The machine of claim 8 including two pairs of dish springs, the backsurface of one member of one pair bearing against the back surface ofone member of the other pair.

10. A cross roll machine comprising a housing;

upper and lower roll carrier means supported in said housupper and lowerrolls supported by said roll carrier means;

one of said roll carrier means and said housing defining verticallyspaced-apart cooperating surfaces disposed so that a load imposed on aroll tends to move said surfaces together;

a plurality of dish springs between said surfaces; and

means for prcloading said dish springs to maintain a substantiallyconstant spacing between said surfaces under normal load conditions andto collapse said surfaces towards each other under overload conditions.

1. In a roll machine including a housing, a roll carrier frame supported within said housing, and a roll supported by said roll carrier frame, the improvement comprising adjusting means for vertically adjuSting said roll carrier frame; said roll carrier frame and adjusting means presenting vertically spaced-apart cooperating surfaces, and means structurally associated with said surfaces so that the imposition of a load on said roll tends to move said surfaces together; and a plurality of dish spring means between said surfaces having a stiffness sufficient to maintain the spacing rigidly between said surfaces under normal load conditions and to yield under overload conditions.
 2. A cross roll straightener machine including a machine axis along which cylindrical stock is threaded; a plurality of opposed upper and lower rolls of roll pairs arranged longitudinally along said axis, the upper rolls being differently angled with respect to the machine axis than the lower rolls; said machine comprising upper and lower housings for said upper and lower rolls; a plurality of roll carrier frames supported in said upper housing supporting said upper rolls; adjusting means for vertically adjusting said roll carrier frames; said roll carrier frames and adjusting means presenting vertically spaced-apart cooperating surfaces, and means structurally associated with said surfaces so that the imposition of a load on said upper rolls tends to move said surfaces together; a plurality of assemblies of dish spring means between said surfaces, each assembly having a stiffness sufficient to maintain the spacing rigidly between the surfaces under normal load conditions and to yield under overload conditions.
 3. A cross roll straightener machine including a machine axis along which cylindrical stock is threaded; a plurality of opposed upper and lower rolls of roll pairs arranged longitudinally along said axis, the upper rolls being differently angled with respect to the machine axis than the lower rolls; said machine comprising upper and lower housings for said upper and lower rolls; a plurality of roll carrier frames supported in said upper housing supporting said upper rolls; adjusting means for vertically adjusting said roll carrier frames, said adjusting means comprising a vertically extending threaded shank; a nutlike screw box member threaded onto said shank; each of said roll carrier frames comprising a cavity to receive said screw box member; said screw box member defining a lower surface and said cavity defining an upwardly facing seat surface spaced from said lower surface; said roll carrier frames and adjusting means presenting vertically spaced-apart cooperating surfaces, and means structurally associated with said surfaces so that the imposition of a load on said upper rolls tends to move said surfaces together; and a plurality of assemblies of dish spring means between said surfaces, each assembly having a stiffness sufficient to maintain the spacing rigidly between the surfaces under normal load conditions and to yield under overload conditions, and said dish springs being disposed between said roll carrier seat and said screw box member lower surface, and encompassing said adjusting means shank.
 4. The machine according to claim 3 wherein said roll carrier frame further comprises a retaining ring connected to said roll carrier frame to bridge said cavity above the screw box member whereby said member bears against said retaining ring; means between said roll carrier frame and said retaining ring to effect a predetermined amount of precompression of the dish springs on tightening the retaining ring to the roll carrier frame.
 5. The machine of claim 4 wherein said roll carrier frame defines an upwardly facing shoulder further including bolt means fastening the retaining ring to said shoulder, said means to effect a predetermined amount of precompression comprising a plurality of shims between the shoulder and retaining ring.
 6. The machine of claim 4 further including means to prevent the rotation of said screw box member relative to the roll carrier frame.
 7. The machine of claim 2 wherein said stand of rolls includes three roll pairs spaced on close centers for precision straightening, said roll carrier frames each comprising a yoke, said rolls comprising a body and oppositely extending neck portions seated in said carrier frame yokes, the neck portions being of small diameter to permit clearance between said yokes and a workpiece, and limiting the radius of the fillets between the neck portions and roll body to a comparatively small dimension.
 8. The machine of claim 2 wherein said dish springs are annular washerlike members comprising inner and outer circular edges including oppositely facing hollowed and back surfaces between said edges, said members being arranged in pairs with the hollowed surface of one member facing the hollowed surface of another member, and the outer edges of said members being in contact.
 9. The machine of claim 8 including two pairs of dish springs, the back surface of one member of one pair bearing against the back surface of one member of the other pair.
 10. A cross roll machine comprising a housing; upper and lower roll carrier means supported in said housing; upper and lower rolls supported by said roll carrier means; one of said roll carrier means and said housing defining vertically spaced-apart cooperating surfaces disposed so that a load imposed on a roll tends to move said surfaces together; a plurality of dish springs between said surfaces; and means for preloading said dish springs to maintain a substantially constant spacing between said surfaces under normal load conditions and to collapse said surfaces towards each other under overload conditions. 